Hydraulic braking systems for automobiles and/or other mobile vehicles are well known. Traditionally, hydraulic braking systems include a method of brake actuation to engage the vehicle brakes. For example, traditional braking systems use a variety of devices to convert mechanical power into fluid power, in the form of fluid displacement and pressure, to actuate the vehicle brakes. In these braking systems, however, the amount of fluid displacement and pressure supplied to the vehicle brakes is limited. Full power hydraulic brake systems, on the other hand, are capable of supplying larger amounts of fluid displacement and hydraulic pressure directly to the vehicle brakes. As a result, full power hydraulic braking systems are capable of supplying significantly higher braking torques with actuation that is faster than traditional hydraulic braking systems.
FIG. 1 illustrates a simple low-gain pressure output for a conventional hydraulic braking system. The vertical axis represents the percentage of pressure or braking output and the horizontal axis represents the percentage of mechanical actuation (e.g., pedal rotation). As shown in FIG. 1, a significant amount of pedal rotation is required to increase the braking output to high levels. For example, only 25 percent of available braking output or pressure is achieved through 75 percent of mechanical actuation. Conversely, the braking output or pressure is significantly increased as the mechanical actuation increases from 75 percent through 100 percent.
Variable ratios of braking output or pressure have been achieved when electrically controlled devices are utilized in conjunction with traditional hydraulic braking systems. For example, braking systems exist that utilize the electronically controlled device to vary the braking output based upon input received from vehicle control systems, such as, the anti-lock braking system, vehicle wheel sensors, or vehicle speed sensors. However, these systems have several shortcomings.
For example, many existing brake systems that use electronically controlled devices to vary the braking output only are capable of providing a preset output in response to certain vehicle conditions. Furthermore, many existing hydraulic braking systems that utilize electronically controlled devices to vary the braking output rely on a separate boosting mechanism to increase the pressure directly to the brakes. Hence these braking systems are limited in their ability to affect the braking output characteristics of the mechanically produced braking output. As a result, many existing braking systems lack the necessary versatility to accommodate the various situations that are encountered by the driver and that require different braking outputs.
Improvements in the mode of operation of hydraulic braking systems is, therefore, desired.